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| S&S Swan Maintenance - Swan 38 Prop pitch for Maxprop 4 easy |
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Join Date: 16 February 2016
Posts: 3 |
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Swan 38 Prop pitch for Maxprop 4 easy Hello to all, I have a couple of questions ,most likely directed at Lars? I am hauling out my Swan 38 in the next couple of days and wish to install my new prop. It can be fine-tuned once in the water ,but I would prefer to get the rough settings correct before then. The boat is currently in San Francisco Bay and the water is less than warm when diving the prop... The engine is a Yanmar 3YM30 which is rated at max hp/kW of 30/22.1 @ 3600rpm. Continuos output 27hp/20kw @ 3484rpm. I understand best cruising speed for motor efficiency to be around 2800-2900 rpm,which is around 80% of max rpm. The prop is a 16 inch 4 bladed feathering prop and I wish to set forward and reverse pitches,which can be set independently. Are the velocity prediction tables different for a 38 with a one ton rig? Are these tables also available? Has anyone replaced panels in the headliner? My two furthest outboard panels came lose. I was thinking about reapplying them with Velcro strips to allow for their future removal as I have some deck hardware above them on the deckhouse that may need removing/rebidding in the future. Finally,probably also directed at Lars, I would also like an alu builders plaque since my boat is missing it and the bronze one. Nazca is hull 38/008. Built in 1974,but I do not know the day/month. Thank you all for such a great forum and especially to Lars! Fair winds and cheers, Robert 38/008 Nazca
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Join Date: 29 January 2007
Posts: 1018 |
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Dear Robert, the aluminum plaque is available thrugh the S&S Swan Association and what you need in order to know Nazca's delivering details is to send a message to Nautor (spareparts@nautors-swan.com), they are very nice and helpful and will send you details. About the ceilings, yes, I do think velcro is perfect, as there is already velcro in many of the ceilings, just be sure to use stainless steel clips to fix it to the ceiling. I had the very same engine onboard 38/067 Only You, and (with a 15" Max Prop, do not remember the exact pitch, Lars suggested me the correct one -perfect, of course-) I managed to get 6,3/6,5 kn at 2,800 rpm. Fair winds! matteo (47/069 Vanessa) |
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Join Date: 02 January 2008
Posts: 1547 |
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Dear Robert Also the reduction gear ratios, both in forward and reverse, is essential information for the determination of pitches for you. Would you prefer the same performance in both directions?
80% of the maximum achievable rpm loads the engine to about 50% output, this is suitable for cruising.
Enclosed pls find the VPPs for the short rig, the differences are small. Presumably the short rig is well suited to San Francisco Bay conditions?
Kind regards
Lars
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Join Date: 16 February 2016
Posts: 3 |
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Dear Lars, Thank you for the supplied speed table! I knew there was something missing from my prop question: Fwd ratio ---2.21 Rev ratio---3.06 In reverse, I mostly want a good grip to stop the boat when maneuvering around the dock or backing down on the anchor. Thanks again for all your time and expertise. And yes indeed, I am happy to give up so little to have a stout shorter rig especially here in blustery SF bay and gale force winds of the Pacific Northwest. Cheers Robert
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Join Date: 02 January 2008
Posts: 1547 |
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Dear Robert Thank you for the information.
The gear ratios are quite different in fwd and reverse, and this affects the pitch angles.
The recommended forward angle is 16 degrees, reverse 26 degrees. This will give equal thrust both ways, and allows the engine to reach close to nominal rpms.
If this is a new engine it is not recommended to increase the pitch further so the maximum rpm is reduced, the warranty may be voided.
Kind regards
Lars
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Join Date: 16 February 2016
Posts: 3 |
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Dear Lars and Matteo, Thank you for the information,your time and passionate engagement to make this forum truly sans pareil! Cheers, Robert
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Join Date: 25 October 2014
Posts: 9 |
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I have reduced my reverse pitch on my Four Blade Vari Prop following advice from a salty old seadog in the Channel Islands. I was saying that the "Prop Walk" was giving me problems getting into my berth in Elizabeth Marina Jersey. When reversing I now put the engine in neutral when I have some movement backwards, that helped, silly me for not thinking about it before. |
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